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[Bug rtl-optimization/24414] Old-style asms don't clobber memory
- From: "law at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 17 Oct 2005 21:55:29 -0000
- Subject: [Bug rtl-optimization/24414] Old-style asms don't clobber memory
- References: <bug-24414-119@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #5 from law at redhat dot com 2005-10-17 21:55 -------
Subject: Re: Old-style asms don't clobber
memory
On Mon, 2005-10-17 at 21:43 +0000, pinskia at gcc dot gnu dot org wrote:
>
> ------- Comment #4 from pinskia at gcc dot gnu dot org 2005-10-17 21:43 -------
> The flow code was added by Jeff Law back in 1999:
> http://gcc.gnu.org/ml/gcc-patches/1999-03/msg00763.html
>
> Jeff, was there a reason why you mentioned old-style asm as special even though
> GCC never handled or documented there were special before that date?
An old-style asm must be assumed to read, write, clobber, well, just
about anything. Documented or not, that's the only thing that makes
sense.
WHy? Think about it for a little while, an old-style asm provides us
with zero information on what values it uses, what values it sets and
what values it clobbers.
jeff
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24414